1. Field of the Invention
The present invention relates to a disc recording apparatus, in particular, relates to a disc recording apparatus for recording data on a recording medium such as an optical disc and a photomagnetic disk.
2. Description of the Prior Art
Recording apparatuses for recording data on recording media such as optical disks and photomagnetic disks record and reproduce signals to and from recording media in such a way that the heads for use do not mechanically contact with the surfaces of the recording media. Thus, this construction contributes to elongating the service lives of the pickups and to improving the reliability thereof. However, the pickups sometimes cause a track jump due to vibration, shock, and so forth applied from the outside of the apparatuses. If a track jump takes place in the record mode, data which has been recorded may be destroyed or erased. Conventionally, to prevent data which has been recorded from being destroyed and erased, when a track jump takes place in the record mode, the record operation is temporarily stopped and then the data is recorded from the beginning.
In addition, when data which has been recorded cannot be reproduced with high reliability (error free state) due to a defect on the disc surface, the data to be recorded is recorded to a so-called substitute area. This process is hereinafter called the substitute process.
When the record operation is temporarily stopped due to occurrence of a track jump or by the substitute process and then the data is recorded from the beginning, it is preferable to stop inputting the data. However, depending on the type of data, it may be very difficult or impossible to stop inputting the data. In this situation, while the record operation is stopped, the input data is not recorded, but lost. For example, since digital audio data (hereinafter referred to as audio data) is continuously input in a particular sampling period, the data cannot be stopped in the middle of the input thereof. Thus, when the record operation is temporarily stopped, audio data in this period is lost. Although the conventional disc recording apparatuses are provided with memory, this memory is used mainly for processing signals rather than for storing the audio data. This is because the memory for storing the audio data should have a large amount of storage capacity.
Even if the record operation is temporarily stopped or the substitute process is performed, so as to securely store the audio data, a disc recording apparatus which performs record operation, reproduce operation, and seek operation substantially at a very high speed than the data transfer rate may be considered. However, this apparatus is difficult to accomplish from technical and cost points of view.
The applicant of the present invention has proposed an optical disc reproducing apparatus which can obtain continuous reproducing output upon occurrence of a track jump. This apparatus has been disclosed as Japanese Patent Laid-open Publication Serial No. HEI 3-3165. According to this prior art, even if an optical spot jumps to an incorrect track, digital data which has been stored in a memory means can be read in accordance with a first master clock and thereby the reproducing output can be obtained without suspension thereof. In addition, after the optical spot is returned back to the correct track, the optical disc is rotated at a second speed which is higher than the first speed in accordance with a second master clock with a frequency higher than that of the first master clock. In this state, the digital data is read from the optical disc and written to the memory means in accordance with the second master clock. Thus, the amount of digital data which is read from the memory means during the restoration from the track jump is quickly stored to the memory means.
According to the above mentioned related art, although no problem takes place in reproducing data from the optical disk, there are problems in recording data to the optical disk.
When a track jump takes place, the record operation is temporarily stopped and then resumed. However, measures for preventing audio data which has been recorded from being destroyed and lost are required. In addition, measures for securely recording data without loss in the event that the reliability of data stored for a long time is low or in the event that the surface of the optical disc has a defect should be taken.